Dynamic impact of cellulose and readily biodegradable substrate on oxygen transfer efficiency in sequencing batch reactors

Ahmed Shawki Ahmed; Ahmed Khalil; Yuichi Ito; Mark C M van Loosdrecht; Domenico Santoro; Diego Rosso; George Nakhla

doi:10.1016/j.watres.2020.116724

Dynamic impact of cellulose and readily biodegradable substrate on oxygen transfer efficiency in sequencing batch reactors

Water Res. 2021 Feb 15:190:116724. doi: 10.1016/j.watres.2020.116724. Epub 2020 Dec 2.

Authors

Ahmed Shawki Ahmed¹, Ahmed Khalil², Yuichi Ito³, Mark C M van Loosdrecht⁴, Domenico Santoro⁵, Diego Rosso⁶, George Nakhla⁷

Affiliations

¹ Department of Civil and Environmental Engineering, Western University, London, ON, N6A 5B9 Canada.
² Department of Mechanical and Materials Engineering, Western University, London, ON, N6A 5B9 Canada.
³ HORIBA Advanced Techno,Co. Ltd., Kyoto 601-8551 Japan.
⁴ Dept. Biotechnology, Delft University of Technology, van der Maasweg 9, 2629 HZ Delft, Netherlands.
⁵ USP Technologies, London, Ontario, N5V 4T7 Canada.
⁶ Department of Civil and Environmental Engineering, University of California, Irvine, CA 92697-2175 USA; Water-Energy Nexus Center, University of California, Irvine, CA 92697-2175 USA.
⁷ Department of Civil and Environmental Engineering, Western University, London, ON, N6A 5B9 Canada; Department of Chemical and Biochemical Engineering, Western University, London, ON, N6A 5B9 Canada. Electronic address: gnakhla@uwo.ca.

PMID: 33310442
DOI: 10.1016/j.watres.2020.116724

Abstract

Aeration is a major contributor to the high energy demand in municipal wastewater treatment plants. Thus, it is important to understand the dynamic impact of wastewater characteristics on oxygen transfer efficiency to develop suitable control strategies for minimizing energy consumption since aeration efficiency is influenced by the biodegradation of pollutants in the influent. The real-time impact of acetate as a readily biodegradable substrate and cellulose as a slowly biodegradable substrate were studied at different operational conditions. Cellulose in the influent wastewater can be removed efficiently using primary treatment technologies, such as the rotating belt filter (RBF). At an ambient DO of 2 mg l^-1 and air flow of 1.02 m³h^-1 (0.6 SCFM), the α-factor was more sensitive to readily biodegradable substrates than to cellulose. On average, α-factor decreased by 48% and 19% due to the addition of acetate and cellulose, respectively. At a DO of 4 mg l^-1 and air flow of 1.7 m³h^-1 (1 SCFM), α-factor remained constant irrespective of cellulose and acetate concentrations. Without active biomass, α-factor decreased by 47% and 43% at a DO of 2 mg l^-1 (air flow of 1.02 m³h^-1) and high DO of 5 mg l^-1 (air flow of 1.7 m³h^-1), respectively. An inverse correlation between α-factor and sCOD was defined and incorporated into a dynamic model to estimate the real-time airflow rates associated with the improvement of the oxygen transfer efficiency due to biodegradation. Finally, the RBF operated with a 158-μm mesh selectively removed cellulose, thus reducing air requirements, and energy by 25%.

Keywords: Activated sludge; Aeration; Cellulose; Off-Gas Test; Oxygen transfer; α-Factor.

MeSH terms

Bioreactors
Cellulose
Oxygen
Sewage*
Waste Disposal, Fluid*
Wastewater

Substances

Sewage
Waste Water
Cellulose
Oxygen